What is a Chicken Egg? (with pictures) What is a Chicken Egg? Last Modified Date: 28 November 2016 Copyright Protected: Top 10 facts about the world An egg is a vessel that contains an ovum — the reproductive cell produced by a female that would nurture and sustain an embryo . A chicken egg is the egg laid by a chicken. In general, eggs are composed of several parts: they have a hard outer shell, which would help protect a growing bird embryo (if the egg is fertilized); and inside the shell is the ovum. In a fertilized egg, a chick grows inside the egg for about 21 days before it is strong enough to break out of the shell and become a “fully-fledged” chicken. In most mammals , ova that are unfertilized are periodically shed with the special lining of the uterus that would help nurture a growing fetus . Fertilized ova stay in place and become part of the building blocks that grows into an infant mammal. Chicken eggs are different in this respect, since hens lay both fertilized and unfertilized eggs, and most of the development of the chicken embryo in fertilized eggs occurs outside of the hen’s body.

Special care of a fertilized egg is required for a chick to grow and hatch. There are two main components of the ova in chicken eggs: the albumen or “white” of the egg and the vitellus or yolk. Most people will note some thick milky white membranous structures in the egg too. When not providing nutrition for growing chickens, these eggs are a source of nutrition for people and for animals that eat them. In fact, of all eggs consumed by people, those from chickens are most common, and recipes calling for eggs tend to mean ones from hens, unless they specify otherwise. Though there are specialty markets that sell emu , ostrich , quail , and duck eggs, these remain a tiny percentage of most eggs purchased by humans. While the chicken was once hailed as perhaps a perfect food for humans, there are some concerns about consuming too many eggs. Though a single egg isn’t tremendously high in calories, the yolks do contain high levels of cholesterol . Some people avoid this issue by simply eating egg whites instead, which are high in protein, although not everyone enjoys eating the whites alone.

There’s also some argument that sources of cholesterol in egg yolks may actually help lower overall bad cholesterol count, though this issue is debated. Most people stick to eating the interior of the egg and either discard or compost the shells. Actually, eggshells are edible, and some people blend them into shakes. Eggshells may also constitute part of chicken feed since they have nutritive value. Different breeds of chickens lay eggs of different colors, but this has no direct impact on the taste or nutritional value of the egg itself. One thing that may prove confusing for people is the different grades of chicken eggs and their different sizes. Eggs come in peewee, small, medium, large, extra-large, and jumbo in the US, although "large" is the most common size used. Moreover, some eggs are labeled organic and others may be sold as created by free-range chickens. The country in which the eggs are produced usually regulates the definitions of each of these terms and grades. Typically, free range and organic eggs will cost most, but the price is usually higher for larger eggs too. Some people purchase fertilized eggs because they’re lower in cholesterol.

Ad SarahSon Post 11 My dad grew up on a farm where they had a lot of chickens. They would gather the eggs, and whatever wasn't needed for their family, they would sell. This is something that many farm families still do today. I have always been kind of afraid of chickens and don't know how comfortable I would be reaching in and grabbing the eggs. This article also reminds me of the age-old question of which came first, the chicken or the egg? golf07 Post 10 It doesn't seem like you hear as much any more about how chicken eggs are so high in cholesterol. Is it the yolk that gives them the high cholesterol content? I always thought eggs were full of good nutrition, and a cheap meal when I was a poor college student. sunshined Post 9 I feel very fortunate to have a neighbor who sells farm fresh chicken eggs. I don't think she can consider them organic or even free range, but I can see how they are fed and taken care of, and feel safe buying eggs from her. I don't usually have any problem getting as many eggs from her as I need.

If there is a big salmonella scare though, people are afraid to buy eggs in the store, and sometimes she runs out of them. andee Post 8 I grew up on the farm and was used to eating brown eggs with bright yellow yolks. Whenever we had overnight guests, they always commented on how yellow our eggs were. I always thought that was a funny comment because that is all I had ever known. Not until I moved to the city and began buying eggs in the store did I realize what they meant. I also realized that the shells on our chicken eggs at home were much thicker and harder to crack. Now I go out of my way to buy brown eggs that are either organic or free range. Some stores carry them, and I can also find some at farmers markets. Sure, I pay more for a dozen of them, but overall, eggs are still pretty cheap when you consider how much nutrition and protein you are receiving from them. giddion Post 7 @kylee07drg – The easiest way is to use a funnel. My friend taught me this trick a few months ago, and it has opened up a whole new world of recipes to me, because I had the same problem as you.

The yolk is too large to go through the narrow hole in the funnel. However, the egg white will slip right on through. Just be sure you have a mixing bowl beneath the funnel to catch the egg white. kylee07drg Post 6 So many recipes, especially desserts, call for egg whites. I have always had trouble separating them from the yolks, so I just avoid these recipes. Can anyone tell me what the best way to separate an egg white from a yolk is? I can't do it using just the shells like some people can. seag47 Post 5 Some people think it's a little weird to cook chicken and eggs together, but I do it all the time. I dip raw chicken in eggs and milk before rolling it in seasoned flour and frying it. My husband also makes an excellent chicken teriyaki meal that uses both chunks of chicken and bits of scrambled egg. It's so delicious, and you might not think this would be true, but chicken and eggs taste great together! healthy4life Post 4 My mother actually got to witness hatching chicken eggs when she was young.

Her family raised their own chickens, and they ate some of the eggs, but the ones they didn't eat got to develop into more chickens. It seems a little unsanitary to eat something that a chicken has been sitting on top of for awhile. I try not to think about this while eating scrambled eggs! DFMeyers Post 2 @liveoak- I know what you mean about not having a clue about eating the shells. I could even grind up the shells into a powder and put them in soups or other foods. I will also think about how I am going to use the shells the next time I buy eggs. liveoak Post 1 I had no idea that you can eat the shell of an egg. I always thought that they should just be thrown out. To think I have been throwing out something with nutritional value all these years is kind of sad. The next time I see chicken eggs for sale I will definitely try eating the shell in a shake.

Post your comments Common egg quality problems - BackYard Chickens Community Common egg quality problems By: sumi Posted 8/27/13 • Last updated 5/3/16 • 224,395 views • 58 comments Approximately 2% of all chicken eggs has some defect, ranging from minor, barely noticeable faults to downright alarming deformities. So the chances are pretty good that most, if not all flock owners will at some stage find an irregular egg. This article is about the most common egg irregularities and problems and their causes. A few members have asked me if these odd eggs are safe to eat. That depends on the cause of the deformity/irregularity. Most of these eggs, though some may look rather unappetising, are perfectly safe for human consumption. If the cause of the deformity/irregularity is disease or treatment for disease/pest I would play it safe and discard the eggs rather as many drugs given to chickens leaves a residue in their eggs during the withdrawal period (usually 3 weeks).

To help us understand these problems and how they occur, let's first look at how an egg is formed: How an Egg is Formed An egg is formed over a period of about 25 hours. The egg yolks are formed in the hen's ovary. Hens, unlike most animals, have only one functional ovary, the left one. At the time of hatch each female chick will have up to 4 000 tiny ova, from some of which yolks may develop when the hen matures. At any given time, an active layer will have a number of yolks in her ovary, in different stages of development. It takes around 10 days for an egg yolk to mature, after which it gets released into the funnel (infundibulum) where, if live sperm are present, it will be fertilized. This process takes about 15 minutes. Next, the yolk moves down into the magnum, where inner and outer shell membranes are added, as well as water and mineral salts. This process takes about 3 hours. The yolk then moves into the isthmus, where albumen (egg white) is secreted and layered around the yolk.

This process takes about an hour. Next the partly formed egg moves into the uterus, or shell gland, where it will receive it's shell. Initially some water is added, thinning the outer layer of albumen. Then the shell material, mostly calcium carbonate, is added, followed by pigments, if a colored egg is produced. For example a brown, blue or green egg. This process takes about 21 hours. Once this process is complete, the egg passes through the vagina and is laid by the hen. This final process takes less than a minute. For a virtual tour of the reproductive tract, see here: Common Egg Shell Quality Problems 1. White banded egg These eggs are the result of two eggs entering and making contact with each other in the shell gland pouch. When this happens, normal calcification (egg shell formation) is interrupted and the first egg that entered the pouch will get an extra layer of calcium, seen as the white band marking. Causes for this are: - Stress in the flock; - Changes in lighting, for example adding artificial light in the coop to encourage laying over winter; - Diseases such as infectious bronchitis. 2.

Blood on egg shell This can be anywhere from a few spots to a smear to an alarming amount of blood. Causes are: - Small blood vessels ruptured in the hen's vagina from excessive straining. This is more common in young pullets coming into lay and overweight hens; - The hen's age. There is a higher incidence in body checked eggs from older layers. 4. Broken and mended egg These are similar to body check eggs. The egg shell got cracked during the calcification process and mended just before being laid. Cause: - Stress, frights or disturbance during the calcification process. 5. Misshaped or odd shaped eggs These eggs differ from the normal shape and/or size and can be either too large, too small, round instead of oval or has major changes in the shape. Shapes can range from minor, barely noticeable to grossly mis-shaped. Causes are: - Immature shell gland (young layers); - Disturbances and/or stress during the calcification process; - Poor nutrition, for example excess calcium in the hen's diet. 7. Lack of pigment or uneven pigmentation on egg shells The causes for this can be: - Poor nutrition.

A deficiency in any of the main nutrients, protein, minerals etc in the hens' diet can influence shell colour and formation. Zinc, copper and manganese are thought to be especially important in transporting pigment onto the shell. It has been suggested that a magnesium supplement can improve shell colour: - Viral infections. Infectious bronchitis and it's variants, Newcastle disease, egg drop syndrome and avian influenza can cause damage to the oviduct, resulting in loss of shell colour and other problems: - Internal and external parasites. A heavy infestation of roundworms and or capillaria worms as well as red mites, when present as a heavy infestation, can have an adverse effect on egg quality and may cause pale shells; - Drugs. The coccidiostat drug, Nicarbazin, if present in feed, can interfere with egg shell pigmentation; - The hen's age. And older layer will often produce eggs with paler shells, as well as a hen who had been laying intensively over a long period; - Stress. Physical stresses, environmental stresses or nutritional stresses can all interfere with shell pigmentation; - Exposure to sunlight and high temperatures can produce a fading effect on the shell. 8.

Calcium coated egg These eggs have an extra, powdery layer of calcium, covering either the entire egg, or just one end of the egg. Causes are: - Disturbance or stress during calcification process; - Poor nutrition, for example excess calcium in the hen's diet. 9. Speckled eggs Spots or speckles can be either brown or white. They are similar to calcium deposits, except the speckles are smaller. Speckles may or may not be pigmented. Causes are: - Stress or disturbance during calcification process; - Poor nutrition, for example excess calcium in the hen's diet. 10. Shell-less eggs A shell less consists of a yolk, albumen and membrane, but has no shell at all. The egg contents are protected by the outer membrane only. These are often seen in pullets coming into lay.

Causes are: - Immature shell gland (young layer); - Nutritional deficiency, usually lack of calcium and vitamins E, B12 and D as well as phosphorous and selenium; - Certain diseases, such as Newcastle disease, infectious bronchitis, avian influenza, egg drop syndrome; - Exposure to very high temperatures and extremely high or low humidity levels; - An infestation of internal or external parasites, such as worms, mites or lice; - Stress prompting the hen to lay an egg prematurely, before the shell is formed; 14. Yolk-less egg aka fart egg, fairy egg, witch egg, rooster egg or oops eggs These tiny eggs may or may not have a yolk. Yolk-less fart eggs are often called rooster eggs. These little eggs are often much darker than normal, as they spend more time in the shell gland pouch and gets an extra layer or two of pigment. These yolk-less eggs sometimes form when: - The hen's oviduct releases a small piece of reproductive tissue or another small foreign mass enters the hen's oviduct, triggering the regular formation of an egg.

The foreign object will be treated like a normal yolk and enveloped in albumen, membranes and a shell; - Occasionally a hen will also lay a fart egg when something disturbs her reproductive cycle; - Young pullets may lay a fart egg or two when coming into lay and is still getting their reproductive systems in gear. 15. Soft shell eggs These eggs are laid with an incomplete shell, sometimes just a thin layer of calcium. Causes are similar to shell less eggs: - Immature shell gland; - Nutritional deficiencies, usually lack of calcium, vitamins E, B12 and D as well as phosphorous and selenium; - Disease such as infectious bronchitis, avian influenza, egg drop syndrome; an internal or external parasite infestation; - Exposure to very high temperatures and/or very high or low humidity levels; - Egg laid prematurely due to stress or a disturbance during the calcification process; - Damage from toenails, or other sharp objects in the nest box, post laying. 1. Blood spots Can range in severity from a small spot of blood on the yolk to about a spoonful of blood mixed with the egg contents.

Egg yolks form and mature in the hen's ovary and sometimes when the mature yolk is released it may rupture a small blood vessel, the blood released will end up being encased in the shell, along with the rest of the egg contents. Causes of this can be: - Incorrect levels of vitamins A and K in the hen's diet; - Administration of the drug sulphaquinoxaline; - Large amounts of lucerne meal in the layers' diet; - Feeding stale, wet or mouldy feed; - Continuous lighting in the coop; - Feed or snacks containing cottonseed oil; - Ingestion of the weed Shepard's Purse. 5. Double or multiple yolk eggs These are more common with your pullets just coming into lay. This happens when more than one yolk matures and gets released at the same time. As many as 9 yolks have been found in a single egg. 6. Rubbery, cheesy or pasty yolks Are caused by: - Ingestion of crude cottonseed oil; - Severe chilling or freezing of intact egg; - Ingestion of velvet weed and other related species. 7.

White or platinum yolks Can be caused by: - An infestation of cappilaria worms and certain diseases. For example pink or green. Cause: - Spoilage due to Pseudomonas bacteria produces a greenish, fluorescent, water soluble pigment in the albumen. - A green tint to to albumen can also be caused by the presence of high levels of riboflavin (vit B2), which has a yellow green colour. For more information on eggs, egg laying and egg layers visit the chicken behaviors and egglaying forum section. ****```````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````**** A huge "Thank you!" to the members who's pics were used in this article. They are: 1. Banded egg- pic by brierose3 2. Blood on shell - pic by lablover 3. Body checked egg - pic by SpotJL 4. Broken and mended - pic by Naked Farm 5.

Misshaped eggs - pic by CaCO3 6. Calcium deposits - pic by HipEMama 7. Pigmentation egg - pic by Wynette 8. Calcium coated - pic by animal-lover99 9. Speckled egg - pic by Wynette 10. Shell less egg - pic by LaLa Chickie 11. Slab sided egg - pic by Mac14 12. Wrinkled egg - pic by FlagChick 13. Corrugated egg - pic by mike555444 14. Fart egg - pic by sumi 15. Soft shell egg - pic by Liz9910 17. Pic by Wynette 1. Blood spot - pic by Melabella 2. Egg yolk - pic by macylee36 5. Double yolk - pic by bellah1 7. Platinum yolk - pic by Sumi 1. Meat spots - pic by ChickPrincess 1. Second and third pic by Sumi Interesting Facts About Chicken Eggs - BackYard Chickens Community Interesting Facts About Chicken Eggs By: Mrs.

Mucket and BYC Support Posted 2/22/12 • Last updated 3/27/12 • 845,344 views • 174 comments Have you ever wondered how a hen can lay an egg every day? Why some eggs are brown and some eggs are white? How many days an egg takes to hatch? Here are the answers to those questions and many more. Hens and eggs Female chickens are called pullets for their first year or until they begin to lay eggs. For most breeds, around 20 weeks is a typical age for the first egg. Some breeds lay eggs daily, some every other day, some once or twice a week. Some individual hens never lay eggs, due to narrow pelvises or other anomalies. Normal laying routines can be interrupted by molting, winter daylight shortage, temperature extremes, illness, poor nutrition, stress, or lack of fresh water. Hens usually return to normal laying habits when the disruption-causing factor ends or is corrected. Most hens are productive layers for two years before declining in production, but some continue to lay eggs for several years. Hens will lay eggs whether or not they’ve ever seen a rooster.

Roosters are necessary only for fertilization of eggs. Egg development and laying process A female chick is born with thousands of tiny ova, which are undeveloped yolks. Once she reaches maturity, an ovum will be released into a canal called the oviduct and begin its journey of development. At any given time a productive hen will have eggs of several stages within her reproductive system. The eggs most recently discharged from the ovary are just tiny yolks, and the eggs farther down the oviduct are progressively larger and more developed. From the time an ovum leaves the ovary, it takes approximately 25 hours for the egg to reach the vent for laying. During that time period, the yolk will grow larger while being surrounded by albumen (egg white), wrapped in a membrane, and encased in a shell. Pigment is deposited on the shell as the last step of the egg production process. If sperm is present, the yolk will be fertilized before the albumen is deposited. As a chick embryo develops in a fertilized egg, the yolk provides nourishment and the albumen cushions the embryo.

Although a hen has only one exterior opening (the cloaca or vent) for egg laying and elimination, eggs are not contaminated during the laying process. Two separate channels, the oviduct and the large intestine, open into the cloaca. As the egg nears the end of the oviduct, the intestinal opening is temporarily blocked off. The egg passes through the cloaca without contact with waste matter. The typical interval between eggs laid is about 25 hours, so a hen that lays an egg every day will lay a bit later each day. Hens don’t usually lay eggs in the dark, so once a hen’s laying cycle reaches dusk time, she will usually not lay till the following morning. Eggshell production drains calcium from the hen’s body. The comb, wattles, legs, and ear lobes will fade as the calcium leaches out. Calcium must be replenished through either feed containing calcium, supplements such as oyster shell, or high amounts of calcium in the soil of birds with outdoor access. Egg variations Young pullets often lay malformed eggs before getting established in a normal laying routine. Older hens may occasionally lay abnormal eggs due to age, stress, or illness.

Pullet eggs--the first ones produced by each pullet--are smaller than the eggs that the same hen will produce as an older hen. “Fart egg” and “oops egg” are terms for tiny eggs that quickly pass through the oviduct without reaching full size. Shell-less eggs are released before they have time to develop a shell. They may have membrane holding them together or just be loose yolk and white. Double eggs or “egg in an egg” are created when an egg with a shell is encased by the next egg in the oviduct and a shell is produced over the outer egg as well. Double yolkers may have a normal amount of egg white with two or more yolks. In the shell, the egg may be unusually large. Yolkless eggs, also called no-yolkers, dwarf eggs or wind eggs, consist of egg white alone. Occasionally an egg will come out with a wrinkly, misshapen, rough, bumpy, or unusually colored shell. Egg size is dependent on breed, age, and weight of the hen. Larger chicken breeds tend to lay larger eggs; banty breeds lay small eggs.

Older hens tend to lay larger eggs than younger hens. The shell color is a breed characteristic. Most chicken breeds lay light-to-medium brown eggs. A few breeds lay white, dark brown, green, blue, or cream colored eggs. Shell color is only “skin deep”-- the eggs inside are the same as eggs of other colors. The shell color intensity of eggs laid by one hen can vary from time to time, with an occasional darker or lighter eggshell. While most eggs have a slight sheen to the shell, some breeds or individual hens tend to lay eggs with a chalkier texture. Chicken-and-egg behavior Most hens will lay eggs in the same nest box as flockmates, so it’s not necessary to have a nest box for each hen. Some hens like to lay their eggs in private and others will join their sisters in the nest box. Often two or three hens will crowd into one box while another nest box remains empty. Sometimes a hen will sit on previously laid eggs and add her egg to the clutch. Another might prefer to sit in another area and deposit one egg by itself. Often a hen will sing “the egg song” before or after she lays an egg.

Some will sing during the process of laying. It is a cheerful song that seems to be a proud announcement. Chickens learn by example, so a fake or real egg left in a designated nest box may encourage hens to lay there instead of on the floor or outdoors. Unconfined hens may lay eggs anywhere outdoors if they don’t want to return to the nest box. Sometimes a free-ranging hen will go missing and reappear weeks later with a parade of chicks. Chickens like to eat eggs, even their own. An egg that gets accidentally broken will likely be eaten by one of the chickens. If you occasionally find pieces of shell or egg yolk in the nest box, it’s usually nothing to be concerned about. Some chickens become habitual egg-eaters that break eggs open and eat them. An egg-eater should be culled from the flock if you wish to have eggs for the kitchen. Not only will that chicken continue to eat eggs, but others will learn from watching and you may end up with several egg-eaters. Holes in eggs and cracked eggs do not necessarily mean there is an egg-eater in the flock.

A hen can accidentally crack an egg in the nest when she sits down or adjusts the nest to lay her own egg. Sometimes curiosity or boredom leads a chicken to peck at an egg without the intention of eating it. Chickens can be fed their own or other eggs either raw or cooked. Eggs provide protein and the calcium in the shell is beneficial for laying hens. A potato masher can be used to break boiled eggs into pieces of egg and shell. Empty eggshells from the kitchen can be fed back to chickens as a calcium supplement without concern for developing egg-eaters. However, to be safe, crushing the shells or running through a blender is a good idea. Chicken birds and bees The only reason a rooster would be required with a flock of hens is to fertilize eggs. As a side job, a good rooster also serves as a watchman, warning his hens of predators and other dangers. He also seeks out food for his harem. Even with a virile rooster in residence, not all eggs will be fertile. Some hens just don’t interest a rooster and others never get caught. Often, roosters will have favorite hens that get most of their attention and others remain unnoticed.

Hens do not have an estrus cycle. They can mate and develop fertile eggs at any time. Sperm can remain viable in the hen’s oviduct for three to four weeks, so one mating will fertilize numerous eggs. Brooding and hatching A broody hen of any breed can be used to hatch eggs and raise chicks from other hens of any breeds. A broody will sit on any eggs, whether or not they are fertile and regardless of who laid them. To gather a suitable clutch of eggs, she will not only lay her own eggs but may roll other hens’ eggs into her nest. While a hen is brooding, you can remove daily any extra eggs she gathers into her clutch. Drawing pencil “equator” lines around the eggs you want her to brood will help with identification. A setting hen will usually leave the nest at least once a day to eat, drink, and defecate. The eggs are not in danger of cooling off too much during a normal foray into the coop or run. Typically, chicken eggs hatch about 21 days from the beginning of incubation or nesting by a broody hen.

A few days early or late is not unusual, and some breeds lean toward earlier or later hatches. Not all fertile eggs will develop into embryos. Some never develop due to egg deficiencies or temperature fluctuations. Not all chick embryos will successfully hatch. They can die any time before hatching, even after pipping a hole in the egg. Double yolk eggs rarely hatch due to crowding during embryo development. If a broody hen has pushed an egg out of the nest, she probably knows something is not right with that egg or embryo. In the kitchen A normal fresh egg has a yellow yolk, a layer of thick albumen (egg white) surrounding the yolk, and a thinner layer of albumen surrounding that. At opposite sides of the yolk are two chalazae, short white twisted strands of albumen that anchor the yolk to the white. A large chalaza does not indicate embryo development. Every egg yolk has a white disc called a blastoderm. It is usually visible but may be very pale. In an infertile egg, the blastoderm is solid white. In a fertile egg, the disc has a faint or distinct ring that makes it look like a donut or bulls-eye.

Fertile eggs are completely edible. In fact, some people consider fertile eggs more nutritious than infertile eggs, but scientific research does not confirm this. Fresh fertile eggs collected daily will not have embryos in them. Embryos do not begin to develop unless the eggs are in a favorable warm environment under a broody hen or in an artificial incubator. The yolk of a chicken egg may be any shade from pale yellow to orange, depending on what the hen has eaten. The color is usually consistent if hens are fed only one type of feed, but foraging hens and those fed kitchen scraps will often produce a variety of yolk colors. The egg yolk or egg white may have red or brown specks in it. These “blood spots” and “meat spots” are harmless bits of tissue and are allowed in commercial Grade B eggs. If they look unappealing, the spots can be removed with a spoon or knife before cooking. An eggshell has a protective coating that prevents bacteria from entering the egg. To retain this coating, eggs should not be washed until just before use. Some eggs are soiled with blood from minor tissue damage or mud or feces from the nest box.

This can be wiped off carefully; the shell should be thoroughly dried. If you aren’t sure how old an egg is, you can submerge it in water. The freshest eggs will remain at the bottom of the container, while old eggs will float. Floaters should either be discarded or opened far from your nose. That’s about all I know about eggs. Now maybe you can help me answer one more question. How can I get my hens to lay golden eggs? Those geese owners have it made. The avian egg - Poultry Hub The avian egg Home > Physiology > The avian egg Humans and other animals have used eggs as a food source for millennia. Eggs are an important and well-balanced source of essential nutrients. Bird eggs (for example, chicken eggs) consist of a protective eggshell, albumen (egg white), and vitellus (egg yolk), contained within various thin membranes. Egg yolks and whole eggs are a good source of protein and choline. For this reason, the United States Department of Agriculture (USDA) categorises eggs as Meat. Chicken eggs that are produced commercially for eating have not been fertilised by a rooster and, therefore, cannot develop into chickens.

It is possible to enrich table eggs with minerals (e.g. iron and iodine), antioxidants (e.g. selenium, vitamin E) or omega-3 fatty acids and vitamins, by adding these as components of the hen diet. There are some enriched eggs available in Australia but this represents a niche market for eggs, as only a small percentage of consumers purchase such eggs. Chicken Egg biology Nature’s role for the egg is as an incubation chamber for the developing chicken. For an egg to develop into a chicken, it needs to have been fertilised by a rooster (also called a cockerel). Once the fertilised egg is laid, it must be kept warm and this may be done naturally by the hen sitting on the egg, or artificially by placing the egg into an incubator. Cross-sectional diagram of an avian egg Diagrammatic side view of the egg shell Ovary and oviduct Cross Section of an egg as incubator The egg contains all the nutrients that the developing chick needs during the three week incubation period and also for the first couple of days after hatch. Water vapour and gases such as oxygen and carbon dioxide are able to move across the egg shell through small openings called pores.

The developing chick starts off as a single fertilised cell on the surface of the yolk and progressively grows, using up the yolk, some of the albumen and some calcium from the inside of the egg shell. In the final stages of development, the chick takes up the last bits of yolk into its own digestive system. Eggs Vary in Colour The production of the bird egg consists of a series of steps that occur as the egg enters and passes along the hen’s reproductive tract (oviduct). The yolk of the egg enters the top of the oviduct and passes into the infundibulum where it spends about 15 minutes. A membrane is added around the yolk and, if the hen has been inseminated, fertilisation occurs in this section of the oviduct. The yolk then spends about three hours in the magnum where the egg white is formed and then one hour in the isthmus where the shell membrane is laid down. The main part of the egg shell is formed in the tubular shell gland and the shell gland pouch which takes about 20 hours.

The egg shell is sometimes referred to as a bio-ceramic because it is made up of calcium carbonate with an organic matrix running through it. Composition of the chicken egg The physical composition on the avian egg can be seen in Table 1, below. The egg is comprised of 32-35% yolk, 52-58% albumen and 9-14% shell. Composition of the albumen and yolk are further presented in the image gallery above (Cross-sectional diagram of an avian egg). Table 1. Nutrient composition of the egg (%) Egg components 0.0009 0.0053 – 0.011 Adapted from Li-Chan, ECY, Powrie, WD and Nakai, S (1995) The chemistry of eggs and egg products, In Egg Science and Technology, WJ Stadelman and OJ Cotterill (Eds), The Haworth Press Inc, New York. A raw egg Yolk Yolk provides the lipids and proteins that are required for embryonic growth.

The yolk is comprised of 33% lipid, 17% protein, and small amounts of minerals, vitamins and carbohydrates. The lipid composition of the egg yolk consists of various lipids and fatty acids, of which the triglycerides represent more then two thirds of the total lipid content (Table 2). Yolk pigmentation is mainly a result from the direct transfer of pigments in feed and/or feed additives, but there is also some endogenous pigment used to colour the yolk. It has been speculated that this endogenous pigment is from body tissues, but the mechanism of storage or release of the pigment is not fully understood. Table 2. Lipid composition of the egg yolk Lipid Composition Polyunsaturated fatty acids 3 – 5 Adapted from Larbier, M and Leclercq, B (1994) Nutrition and feeding of poultry, Nottingham University Press, Nottingham. Egg yolk colour Egg yolk colour In Australia, people like a yolk that is bright yellow-orange. Europeans like their egg yolks even darker whereas, in North America, paler yolks are the norm.

Fifty years ago, most people had a few chickens in the backyard, even if they lived in a city. These chickens would often be fed only on table scraps and what they could scavenge in the back yard. They would eat many types of plants which are a source of a group of pigments known as carotenoids. These get laid down in the egg yolk and give it a bright yellow-orange colour. As far as is known, these pigments do not contribute to the nutritional value of the egg. When egg production became more intensive and laying hens were fed a complete diet, egg producers added carotenoids to the poultry feed to produce the bright-coloured yolks that people were accustomed to from the back-yard hen days. In the commercial egg industry in Australia, most egg producers use a synthetic form of carotenoid. It is possible to obtain natural pigments, which are produced from plant products such as marigold flower petals or red capsicums, but these are more expensive than the synthetic pigments. The grains fed to chickens contain some carotenoids particularly from corn (maize) which is commonly used in poultry diets in North America.

In commercial free range production, it is usual to add carotenoids to the feed also. Albumen The albumen consists chiefly of proteins, including ovalbumin, ovotransferrin, ovomucoid, ovoglobulin, lysozyme and ovomucin (See Table 3). The various roles of these proteins include inhibition of protein break down, and maintenance of the viscosity of the thick albumen. The function of the albumen is to protect the embryo (or yolk) from attack by microorganisms and to serve as a source of water, protein and minerals for the embryo. There are four distinct layers of albumen that surround the yolk by the time the egg is laid. The innermost layer is known as the chalaziferous layer (attached to the yolk) (2.7% total albumen), followed by the inner thin layer (16% total albumen), the middle thick layer (50% total albumen) and the outer thin layer (25% total albumen).

The majority of the modifications to the albumen occurs during the first 6-8 hours (2-3 hours in modern layers), after which the developing egg enters the shell gland and undergoes a process called ‘plumping’. During this process a uterine secretion, which is mostly water with some minerals such as sodium, calcium and potassium, is pumped into the egg. Table 3. Protein composition of the egg albumen Principal Protein Content Science of Eggs: Egg Science | Exploratorium Experiment with heating eggs by hard cooking eggs , by making deviled eggs , or by making flan . Beat em When you beat raw egg whites to make a soufflé or a meringue, you incorporate air bubbles into the water-protein solution. Adding air bubbles to egg whites unfolds those egg proteins just as certainly as heating them. To understand why introducing air bubbles makes egg proteins uncurl, you need to know a basic fact about the amino acids that make up proteins. Some amino acids are attracted to water; theyre hydrophilic, or water-loving. Other amino acids are repelled by water; theyre hydrophobic, or water-fearing. Egg-white proteins contain both hydrophilic and hydrophobic amino acids.

When the protein is curled up, the hydrophobic amino acids are packed in the center away from the water and the hydrophilic ones are on the outside closer to the water. When an egg protein is up against an air bubble, part of that protein is exposed to air and part is still in water. The protein uncurls so that its water-loving parts can be immersed in the waterand its water-fearing parts can stick into the air. Once the proteins uncurl, they bond with each otherjust as they did when heatedcreating a network that can hold the air bubbles in place. When you heat these captured air bubbles, they expand as the gas inside them heats up. Treated properly, the network surrounding bubbles solidifies in the heat, and the structure doesnt collapse when the bubbles burst. Experiment with foaming egg whites by making Pavlova . Mix em up Everyone knows that, left to their own devices, oil and water dont mix. But for many recipes, you mix oil-based and water-based liquids—and want them to stay that way. Often, egg yolks come to your rescue by creating an emulsion.

Most food emulsions are known as the oil-in-water type, which means that oil (or fat) droplets are dispersed throughout the water. Put oil and water in a jar, shake it vigorously, and youll disperse the oil. To prevent the oil droplets from coalescing, however, a substance known as an emulsifier is required. Egg yolk contains a number of emulsifiers, which is why egg yolks are so important in making foods such as hollandaise and mayonnaise. Many proteins in egg yolk can act as emulsifiers because they have some amino acids that repel water and some amino acids that attract water. Mix egg proteins thoroughly with oil and water, and one part of the protein will stick to the water and another part will stick to the oil. Lecithin is another important emulsifier found in egg yolk. Known as a phospholipid, its a fatlike molecule with a water-loving “head” and a long, water-fearing “tail.” The tail gets buried in the fat droplets, and its head sticks out of the droplet surface into the surrounding water.

This establishes a barrier that prevents the surface of the fat droplet from coming into contact with the surface of another fat droplet. Experiment with mixing oil and water by making hollandaise sauce . Science of Eggs: Anatomy of an Egg | Exploratorium SHELL Bumpy and grainy in texture, an eggshell is covered with as many as 17,000 tiny pores. Eggshell is made almost entirely of calcium carbonate (CaCO3) crystals. It is a semipermeable membrane, which means that air and moisture can pass through its pores. The shell also has a thin outermost coating called the bloom or cuticle that helps keep out bacteria and dust. INNER AND OUTER MEMBRANES Lying between the eggshell and egg white, these two transparent protein membranes provide efficient defense against bacterial invasion. If you give these layers a tug, you’ll find they’re surprisingly strong. They’re made partly of keratin, a protein that’s also in human hair. AIR CELL An air space forms when the contents of the egg cool and contract after the egg is laid.

The air cell usually rests between the outer and inner membranes at the egg’s larger end, and it accounts for the crater you often see at the end of a hard-cooked egg. The air cell grows larger as an egg ages. ALBUMEN The egg white is known as the albumen, which comes from albus, the Latin word for “white.” Four alternating layers of thick and thin albumen contain approximately 40 different proteins, the main components of the egg white in addition to water. CHALAZAE Opaque ropes of egg white, the chalazae hold the yolk in the center of the egg. Like little anchors, they attach the yolk’s casing to the membrane lining the eggshell. The more prominent they are, the fresher the egg. VITELLINE The clear casing that encloses the yolk. YOLK The yolk contains less water and more protein than the white, some fat, and most of the vitamins and minerals of the egg. These include iron, vitamin A, vitamin D, phosphorus, calcium, thiamine, and riboflavin. The yolk is also a source of lecithin, an effective emulsifier.

Yolk color ranges from just a hint of yellow to a magnificent deep orange, according to the feed and breed of the hen.

Question: What is the common name for the part of the chicken egg known as the albumen?
Answer: Egg white